Fig. 2

Schematic of the different cell types in the prostate and their identifying markers. The epithelial compartment is composed of three basic cell types: basal, luminal, and neuroendocrine cells, and two intermediate phenotypes. Basal cells are non-secretory cells located along the basement membrane of the epithelium and are characterized by the following markers: ΔNp63 (a member of p53 transcription factors family) [150], cytokeratins 5 and 14 (CK5 and CK14) [151, 152], CD44 [153], integrin α₂β₁ [65], integrin α₆β₁ [154, 155], CD133 [65], CD117 [66], Sca-1 [66, 156], CD49f [157], and tumor-associated calcium signal transducer 2 (Trop2) [157]. Basal cells give rise to secretory luminal cells by transitioning through intermediate states. Two intermediate phenotypes have been described: (1) transit-amplifying cells which are non-secretory and exhibit a more basal-like phenotype and (2) intermediate cells which are secretory and exhibit a more luminal-like phenotype. Both, transit-amplifying and intermediate cell types may express cytokeratin profiles similar to basal or luminal cells, however, only transit-amplifying cells have been shown to express CD24 to distinguish them from low differentiated basal cells [158] and only intermediate cells have been shown to express CK19 to distinguish them from luminal cells [159]. Luminal cells are secretory columnar cells that express high levels of androgen receptor (AR), cytokeratins 8 and 18 (CK8 and CK18), and prostatic acid phosphatase (PAP) [160]. Lastly, neuroendocrine cells are very rare cells located in the luminal layer and represent less than 1% of the prostatic epithelium. They are non-secretory, differentiated cells that express chromogranin A (CgA), CD56, synaptophysin, calcitonin, and neuron specific enolase (NSE) [161, 162]. This figure has been adapted from diagrams in related literature [163,164,165]